The present invention relates to a multilayer pipe made of elastomeric material, and in particular for feeding high-pressure fuel from a pump to a vehicle engine.
As is known, vehicle fuel feed pipes are made of thermoplastic or elastomeric material, and preferably comprise a number of layers of materials of different chemical compositions. For safety reasons, a multilayer petrol pipe must be impermeable to petrol vapor, resistant to both high and low temperatures, and flame-resistant.
Pipes made of elastomeric material normally comprise an inner layer, a reinforcing layer of plastic fibres, and a cover layer of elastomeric material.
Such pipes are used widely on account of the inner layer of elastomeric material, which simplifies connection by not requiring the special seals required by corresponding pipes of thermoplastic material, and on account of the excellent high-temperature and flame resistance of the outer layer.
Such pipes also feature a barrier layer to prevent permeation by fuel vapor.
Pipes have been proposed in which the inner layer is made of fluorinated rubber, e.g. VITON(copyright), and the barrier layer of TEFLON(copyright). The mixtures forming the inner layer, however, pose problems in cold working conditions, while the pipes themselves are extremely expensive to produce.
Modern direct-injection systems also call for feeding high-pressure fuel, e.g. of over 100 bar. So far, this has been done using metal pipes capable of withstanding high pressure, while at the same time being impermeable to vapor. Being substantially rigid, however, metal pipes pose problems in terms of vibration resistance, provide for substantially no damping of pulsating pressure, are difficult to fit, and condition design of the engine compartment.
It is an object of the present invention to provide a pipe capable of substituting currently used low-pressure-resistant plastic pipes, but which may also be used at pressures of over 100 bar to also substitute metal pipes, and is therefore impermeable to petrol vapor, resistant to high and low temperatures, flame-resistant, and flexible.
According to the present invention, there is provided a multilayer pipe for conducting hydrocarbons, and comprising at least one inner layer of elastomeric material; a barrier layer; a reinforcing layer made of spun fabric comprising fibers; and a cover layer of elastomeric material; wherein said barrier layer comprises at least one polyamide.
In particular, according to a preferred embodiment of the present invention, there is provided a multilayer pipe including at least one inner layer comprising a material selected from the group consisting of acrylonitrile/butadiene, hydrogenated acrylonitrile/butadiene, chlorosulfonated polyethylene, and EPDM; a barrier layer comprising a material selected from the group comprising aliphatic or aromatic polyamides, polyamide mixtures, and polyamide-polyolefin mixtures; a reinforcing layer of spun fabric comprising fibers of a material selected from the group consisting of aliphatic polyamides, aromatic polyamides, and polyesters; and a cover layer comprising a material selected from the group consisting of chlorosulfonated polyethylene, chlorinated polyethylene, acrylonitrile/butadiene and PVC mixtures, epichlorohydrin, EPDM, chloroprene, EVA and EVM.